Overview#
There are many route types defined for EVPN. Not all route types are supported by all vendor implementations. I’ll cover the first 5, since they are the most important.
Type 1: Auto Discover Segment Route#
- Advertise the existence of Ethernet segments network-wide
- Required when an edge device is multi-homed
- Help avoid loops and ensure that only required multicast traffic is delivered to the pertinent Ethernet segments
- Carry an attribute called the Ethernet Segment Identifier (ESI) which is used for active/active multi-homing
Type 2: MAC-IP Route#
- Advertise locally learned/provisioned MACs to their specific Ethernet segments
- Accompanied by a route distinguisher
- Optionally, can advertise IPs which are endpoint /32s
- Support unicast and broadcast
- Support virtual machine MAC migration
Type 3: Inclusive Multicast Ethernet Tag (IMET) Route#
- Used to advertise the list of VNIs connected behind a certain VTEP so that other VTEPs can dynamically build the flood lists for BUM traffic
- Also possible to create flood lists manually, but please don’t
- An IMET route sets up a path for broadcast, unknown unicast, and multicast (BUM) traffic between VTEPs on a per-VLAN, per-EVI basis
Type 4: Ethernet Segment Route#
- An Ethernet segment identifier (ESI) allows a device to be multi-homed to two or more VTEPs in single/active or active/active mode
- Advertises the reachability of ESIs
- VTEP that are connected to the same Ethernet segment discover each other through the ESI
Type 5: IP Prefix Route#
- Extends EVPN’s capabilities to Layer 3 by allowing the advertisement of IP prefixes over the EVPN network
- In the control plane, EVPN Type 5 routes are used to advertise IP prefixes for inter-subnet connectivity